package com.itheima.demo;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ListDemo {//List的增删改查
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        Collections.addAll(list, "aaa","bbb","ccc");

        //增
        list.add(0,"ooo");
        //删
        list.remove(1);
        //改
        list.set(1,"123");
        //查
        System.out.println( list.get(2));
        System.out.println(list);
        //黑马每天的学费
        System.out.println(((double)20000/30/5));
    }
}
